Putting it that way, it doesn't at allMaybe its a 20th century thing but Kirk agreeing with the mother to have nothing to do with his own child...which writer thought that would paint him in a good light?
As for having an unplanned pregnancy, you mean birth control still fails in the 23rd century? LOL

Though I always took it as a "I dont want him idolising Starfleet. Because I dont believe in it." type thing, which is a bit deeper an issue and a bit more understandable from both sides.